Method of color photography



April 1941- L D. MAN| 1Es ETAL 2,238,495

METHOD COLQR' PHOTOGRAPHY Filed April 12, 1940 EMULSION mm COUPLER INCORPORATED AT /1' 6.5 ORLESS. I WPPORI BLUE SENSITIVE EMULS/O/Y.

/4 ,5 mm, mm. /3 GREEN SENSITIVE EMULSION. /2 R50 JENSIT/VE EMULSION.

V v 1.9 W -AMMOMA 6A5.

' I v ACID COUPLING DEVELOPER.

LEOPOLD D. MANNES LEOPOLD GODOMSKYJQ. INVENTORS Patented Apr. 15, 1941 UNITED STATES PATENT OFFICE a .z,z:s,4s

Leopold n. God

Marines, New York, N. Y., and Leopold owsky, In, Weltport, Conn, assignors to Eastman Kodak Company, Rochester, N. Y., a corporation ot New Jersey Application April 12, 1940, Serial No. 329,344 7 n Great Britain May 10, 19:9 I

6Claims.

'lhis invention relates to an improved method emulsion on a support while maintaining the pH of such emulsion on the acid side of neutrality during such incorporation and such coating.

3 In the accompanying'drawing, Fig. 1 is a sectional view of a single layer photograpic element made'according to our invention, Fig. 2 is a-sectional view of a multi-layer photographic element.

madeaccording to our invention and Fig. 3 is a view, partly in section, of apparatus used in the treatment of film according to our invention.

The invention particularly includes the method of producing a multi-layer sensitive color-photographic element by coating a plurality of gelatinoincorporating in the photographic silver halide emulsion before or after exposure a compound which couples, during development, with the oxi-.

dation product of the developing agent, and forms a coloring substance which is likewise .deposited adjacent the silver grains of the silverimase during development. Such a compound, which is employed in conjunction with a developing agent for the silver and which couples with the oxidation product thereof during development, is referred to herein as a color coupler. 7

It isknown that when color couplers are incorporated in the photographic emulsions themselves diiliculties arise through the fact that these color formers tend'to wander from the emulsion in which they are incorporated during the coating 7 of the; emulsions on a support and during processing operations, iniwhich the emulsions are silver salt emulsion layers on a single support in which a color coupler is incorporated in at least one of the emulsions before coating and the pH of such emulsion is maintained on the acid side of neutrality during such incorporation and such coating.

Preferably, the emulsion is maintained at a pH below 6.5, more particularly, below 5.5 during such incorporation and coating.

The invention also includes a color photographic element having a support and at least one layer ll coated on such support (Fig. 1),

' which layer consists of a gelatino-silver salt treated with liquid baths such as developing baths andir flxing baths. Many proposals have been made .which have had for their object to prevent or retard the'wandering of the color couplers, e. g. by employing couplers containing 'in the molecule group intended to render the color couplers non- It has now been found that the color couplers 1 show very much lesstendency to wander in acid solutionsv than in alkaline solutions and that ii.

the emulsions containing them are so prepared,

emulsion in which a color coupler has been incorporated while maintaining the pH of the-emulsi0n 0n the acid side of neutrality during the incorporation of the color coupler and coating on the support.

More particularly, the invention includes a multi-layer color photographic element in which 7 two or more emulsion layers are inseparably coated on asingle support I 0 (Fig. 2) each'consisting of a gelatino-silver salt emulsion in which a color coupler has been incorporated while'maintaining the pH of the emulsion on the acid side of neutrality during the incorporation ofthe color coupler and coating .on the support. Such 1 multi-layer color photographic element may have V and processed that they are never subjected to liquid baths other than those which are c;- an acid character until the coupling development has taken place, those color couplers which will diiluse under alkaline conditions can, nevertheless, be used without \mdue diirusion taking place. 7

Aecording toone graphic which a colored image can be produced by development of a silver salttherelneonslstsinin': -acol0rcouplerina gelatin-sliver salt feature of the presentinvention, the methodot producing a sensitive photo-.

, and coatins such three emulsion layers l2, l3 and I4 respectively sensitized to blue, red and'greenregions oi the v spectrum. The element may include the'usual Q 7 yellow filter layer 15 between emulsion layers It and I. The invention also includesthe method Y or ,a photograph element consistin 0! a support having coated thereon at least one silver salt emulsion layer containing a'color coupier in which any processing baths to which the j element is subjected which are not intended to bring about reaction of the colorcoupler are maintained on the acid side. or neutrality, and

development with a color-forming developer is carried out without immersion of the element in an alkaline liquid.

The development with a color-forming developer may be carried out by causing the emulsion layer or layers which contains or contain the color coupler to imbibe a color-forming developer of acid reaction and then treating it or them with the alkali necessary for development and coupling without immersion in liquid. Such treatment with alkali can be eiIected conveniently by bringing the moist and swollenemulsion into contact with ammonia gas. The three difi'erentially-color sensitized layers may or may not be separated by gelatine intermediate layers. The emulsion may be silver bromide or silver chloride, or some may be of silver chloride and some of silver bromide. Thus, the two lowerlayers may be silver chloride emulsions and the upper layer a silver bromide emulsion, the choice of the material depending upon whether the element is to be used for camera exposure or printing. 7

The color couplers are incorporated in the layers before coating by mixing them with the respective emulsions while maintaining such emulsions at a low pH, i. e. on the acid side of neutrality and preferably below 6.5, most desirably below 5.5. The color couplers may be any of the color formers known and described in the literature, e. g. phenols, naphthols, compounds containing a reactive methylene group such as acetoacetic esters, pyrazolones, arylacetonitriies and the like. Examples of suitable color couplers (also called coupling components) are acetoacetanilide, p-naphthoyl acetonitrile, and a-hydroxy diphenyl.

At no time during the incorporation of the color coupler in the emulsion or during the coating of the emulsion should the pH be allowed to or above the point of neutrality.

In the case of a film, for example amotion picture film l6 (Fig. 3) which contains the color couplers in three diflerentially color-sensitized layers on the same side of the support, the film may be processed to a negative by bathing it for a short time in an acid solution of acolor developer, for example one of the following formula:

Diethyl paraphenylenediamine hydro- I chloride gms...-

20 Sodium bisulphite do 10 Potassium bromide do 2 Water to make liters 1 In the treatment of a chloride emulsion, the quantity of potassium bromide may be decreased. or this may be replaced by a soluble chloride. The film Ii is immersed in this acid solution of color developer II in tank l'l Just long enough to wet it thoroughly, a time of one minute being usually sufllcient. After immersion the excess of liquid is removed, e. g. by a squeegee 2!.

The film is then brought into contact with ammonia gas in chamber is for a suiilcient time to render it thoroughly alkaline. This causes development to take place. whereby the latent images are developed to silver and simultaneously the color coupler couples with the oxidation product of the developing agent. A few minutes exposure to ammonia gas is sufllcient to cause development to take place, ,5 minutes being adequate in the majority of cases. The ammonia gas is passed through tank It by means of pipes II and ,2l.

After development has taken place the film is washed in a liquid of sufiiciently low pH value to arrest further color development. A weak sodium bisulphite solution having a pH between halide developable. The development of the residual silver halide is then carried out by imbibition of an acid color developer and treatment with ammonia gas as described above.

Instead of using ammonia gas alone, a mixture of ammonia and sulphur dioxide, or of ammonia and carbon dioxide, may be used. In such cases, either ammonium suiphite or ammonium carbonate is formed in the film which may give in some cases more desirable development conditions'.

It will be seen that in the above processing the emulsions are not allowed to come into contact with any liquid baths whole pH values are on the alkaline side of neutrality until the time when color development actually takes place. Moreover, the. development is carried out under such conditions that little molecular diiiusion oi the developer can take place, but this 18 pemfltted to act in the medium of swollen gelatine.

The film treated may carry a sound track which may be processed to minus-red color by recording it in the layer which contains a colorcoupler for minus-red and by developing the image in the sound track area alone by means pf a coupling developer applied by an applicator lroller. The processing of the sound track may proceed any other step in the processing since the acidity of the first developing solution applied for development of the picture areas will arrest further action of the minus-red color coupler.

We claim:

1. The method of forming a colored image in a photographic silver halide layer, which comprises incorporating i the layer at a pH lowerthan' about 6.5 a compound which couples with an aromatic amino developing agent in alkaline solution to form a dye, and which dlfluses from the layer inalkaline solution, exposing the layer to light to which it is sensitive, immersing the exposed layer in an acid solution of an aromatic amino developing agent, and then subjecting the layer ior a short time to alkaline vapors to form a colored image in the layer.

2. The method 01' forming a colored image in a photographic silver halide layer, which comprisesincorporating in the layer at a pl! lower than about 6.5 ii-compound which couples with an aromatic amino developing agent in solution to form a dye, and which diituses from the layer in alkaline solution, exposing the to light to which it is sensitive, immersing the exposed layer in an acid solution 0! an aromatic amino developing agent, and then subjecting the layer for a short time to ammonia vapors to form a colored image in the layer.

3. The method of forming a colored image in a photographic silver halide layer, which comprises incorporating in the layer at a pH lower than about 6.5 a compound which couples with an aromatic amino developing agent in alkaline solution to form a dye, and which diiluscs from the layer in alkaline solution, exposing the bye: to light to which it is sensitive, immersing the :xposed layer in an acid solution of an aromatic imino developing agent, for about one minute, and then subjecting the layer for about five minutes to ammonia vapors to form a colored image in the layer. Y

4. The method of forming a multi-color image in photographic silver halide layers, which comprises incorporating in three superposed layers each sensitive to a difierent region of the visible spectrum, at a pH lower than about 6.5, three diil'erent color couplers which couple with an aromatic amino developing agent in alkaline solution to form dyes and layers in alkaline solutions, exposing the layers to light to which they are sensitive, immersing the layers in an acid solution of an aromatic amino developing agent, and then subjecting the layers for a short time to the action of alkaline vapors to form colored images in the layers.

5. The method of forming a multi-color image in photographic silver halide layers, which comprises incorporating in threesuperposed layers sensitive respectively to the blue, green, and red regions of the visible spectrum, at a pH lower than about 6.5, color coupler forming yellow, magenta, and blue-green dyes, respectively, which couple with an aromatic in alkaline solution to form dyes and which which difluse from the amino developing agent diiiuse from the layers in alkaline solutions, exposing the layers to light to which they are sensitive, immersing the layers in an acid solution of an aromatic amino developing agent. and then subjecting the layers for-a short time to the action of alkaline vapors to form colored I images in the layers.

6. The method of forming a niulti-color image in photographic silver halide layers, which comprises incorporating in three superposed layers sensitive respectively to the blue, green, and red regions of the visible spectrum, at a pH lower than about 6.5, 00101 couplers, forming yellow, magenta, and blue-green dyes, respectively, which couple with an aromatic amino developing agent in alkaline solution to form dyes and which diffuse from the layers in alkaline solutions, exposing the layers to light to which they are sensitive, immersing the layers in an acid solution.

of an aromatic amino developing agent, and then subjecing the layers for a short time to the action of alkaline vapors to form colored images in the layers, and thereafter arresting further color development by immersing the layers in an acid bath.

ILEOPOLD, D. MAmms. moron!) GODOWSKY. JR. 

